1. Field of the Invention
The present invention relates to a method of manufacturing a needle-shaped bristle and a toothbrush manufactured using the same method, and, more particularly, to a method of manufacturing a needle-shaped bristle and a toothbrush manufactured using the same method, in which the needle-shaped bristle has a tip thickness of 0.01˜0.04 mm and a taper length of 2.0˜6.0 mm.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
A method of tapering a polyester toothbrush bristle uses a principle in which, when a polyester fiber is immersed into a heated sodium hydroxide solution, part of the fiber is dissolved. Toray Industries, Inc. disclosed, for the first time, a method of tapering a tip of a bristle, in which a bundle of polyester bristles is cut to a predetermined length, is vertically immersed in a sodium hydroxide solution, having a concentration of 20% and a temperature of 100 or more, to a depth of about 5 mm, and is then dissolved (hydrolyzed), based on this principle (Japanese Examined Utility Model Sho 50-40195).
Further, Korean Patent No. 10-0130932 disclosed a method of tapering a monofilament for a toothbrush, in which a bundle of toothbrush bristles is dissolved in sulfuric acid, having a concentration of 80˜90% and a temperature of 80˜200°, and is thus tapered.
Toray Filament Inc., which is a company affiliated with Toray Industries, Inc., disclosed a technology of manufacturing brushes by implanting bristles, each of which has a taper at one end thereof without folding, or bristles, each of which has tapers at both ends thereof and folded in half, using the above methods (Japanese Unexamined Utility Model Sho 57-12934), and disclosed a method of manufacturing a toothbrush by folding a bristle such that a tapered part of the bristle is relatively long whereas an untapered part of the bristle is relatively short (Japanese Examined Utility Model Sho 61-10495).
Moreover, Toray Filament Inc. disclosed a method of manufacturing a toothbrush by folding toothbrush bristles, each of which has tapers at both ends thereof, in half and implanting them in the head of a toothbrush (Japanese Unexamined Utility Model Hei 05-15834). This method has been widely used.
That is, there has been disclosed a technology of manufacturing a toothbrush by folding toothbrush bristles, each of which has tapers at both ends thereof, in half and implanting them in the head of a toothbrush. The toothbrush bristles are cut to a predetermined size, one end of the toothbrush bristle is dissolved by vertically immersing the tip of the toothbrush bristle into a chemical, and the other end of the toothbrush bristle is dissolved using the same method. The bristle is then cooled, neutralized, cleaned in water and dried, thereby manufacturing the double end tapered toothbrush bristle.
However, the above method has a problem in that a lot of time is required to perform the tapering process. For example, when the tapering process is performed using a sodium hydroxide solution having a concentration of 40% at a temperature of 110°, 80 minutes are required to perform the process of tapering one end of a toothbrush bristle.
In order to solve the problem, the present inventor has completed an invention, which is disclosed in Korean Patent Application No. 10-2006-0103321 (hereinafter, referred to as the “prior art”), relating to “a method of tapering a toothbrush bristle, in which a bundle of cut bristles is preliminarily immersed in a liquid material, and then the entire bundle of bristles is immersed in a chemical, whereby both ends of the bristle are tapered”.
The efficiency of the tapering of the toothbrush bristle is increased about three times using this method. However, this method still has a problem in that the taper length of the toothbrush bristle is about 5˜8 mm, which is similar to that obtained by conventional technologies, and is comparatively long.
In a method of implanting a bristle without using an anchor, which has been widely used in recent years, when the taper length of a toothbrush bristle is 6 mm or more, it is difficult to dissolve the toothbrush bristle because the length of the toothbrush bristle used in the method of implanting a bristle without using the anchor is about ½ of the length of a toothbrush bristle used in the method of implanting a bristle by fixing the bristle using an anchor, which is used in a conventional method. The length of a bundle of toothbrush bristles is short at the time of vertically tapering the bundle of the toothbrush bristle. In this method, it is also difficult to bind the toothbrush bristles using a rubber band after a process of cleaning in water and a drying process because the taper length is relatively long, and it is difficult to produce a toothbrush because the toothbrush bristle does not have desired mechanical properties. Accordingly, in the toothbrush manufactured using the method of implanting bristles without using an anchor, it is required that the taper length of the toothbrush bristle be 6 mm or less, preferably 5 mm or less, and more preferably 4 mm or less.
Meanwhile, after a chemical immersion process is performed, the toothbrush bristle may be processed such that the taper length thereof is 4 mm or less through a mechanical grinding process. However, there is a problem in that needle-shaped bristles formed through this method, as shown in FIG. 1, pierce the gums at the time of brushing the teeth because a taper angle of the needle-shaped bristles is gentle. Further, the needle-shaped bristles formed through this method have problems in that the thickness of the tip thereof is not uniform due to differences of surface contact pressures at the time of grinding, the tip thereof is easily bent, and this bent portion breaks at the time of brushing the teeth.
Further, in the technology for decreasing the taper length of a toothbrush bristle, there have been attempts to additionally use an organic quaternary ammonium salt decomposition promoter. However, there remain problems in that the decomposition promoter is expensive, the toothbrush bristle is yellowed, and the taper length is not shortened to the desired extent.